Laser welding is a process that uses the radiation energy of a laser to achieve effective welding. Its working principle is as follows: a laser-active medium (such as a mixture of CO2 and other gases, YAG aluminum garnet crystal, etc.) is excited in a specific way to oscillate back and forth in a resonant cavity, thereby forming a stimulated radiation beam. When the beam comes into contact with the workpiece, its energy is absorbed by the workpiece, and welding can be performed when the temperature reaches the melting point of the material.
Laser welding can be divided into heat conduction welding and deep penetration welding. In heat conduction welding, heat diffuses into the workpiece through heat transfer, resulting in melting only on the weld surface. The interior of the workpiece is not completely melted, and vaporization is minimal. It is often used for welding thin-walled materials at low speeds. Deep penetration welding not only completely melts the material but also vaporizes it, forming a large amount of plasma. Due to the higher heat output, a keyhole phenomenon may occur at the tip of the weld pool. Deep penetration welding can completely penetrate the workpiece and has high energy input and fast welding speed, making it the most widely used laser welding mode currently.
Advantages of laser welding
① Laser welding can achieve high-quality joint strength and a large aspect ratio, and the welding speed is relatively fast.
②Since laser welding does not require a vacuum environment, remote control and automated production can be achieved through lenses and optical fibers.
③Laser has a large power density, which can achieve good welding effect on difficult-to-weld materials such as titanium and quartz, and can weld materials with different properties.
④ It can perform micro-welding. After being focused, the laser beam can obtain a very small spot and can be precisely positioned, which can be applied to the assembly welding of micro and small workpieces in mass automated production.
Disadvantages of laser welding
① The laser and welding system components are relatively expensive, so the initial investment and maintenance costs are higher than those of traditional welding processes, resulting in poorer economic benefits.
②Because solid materials have a low absorption rate of laser, especially after the presence of plasma (plasma has an absorption effect on laser), the conversion efficiency of laser welding is generally low (usually 5%~30%).
③Because the focused spot of laser welding is small, the equipment precision requirements for the workpiece joint are high, and even a small equipment deviation will produce a large processing error.
Is laser welding harmful to humans?
The laser emitted by welding machines is invisible and has extremely high energy; non-professionals should not come into contact with the laser source, as it is very dangerous. Furthermore, while lasers are electromagnetic waves, the lasers used in welding machines have very long wavelengths, so they do not pose the radiation hazards of short-wavelength light waves such as ultraviolet rays.
Welding produces many gases, but most of them are inert and non-toxic. However, the treatment depends on the welding material. It is best to take protective measures to reduce gas inhalation.
While the laser emitted by a welding machine poses virtually no radiation hazard, the welding process itself generates ionizing and stimulated radiation. It's best to stay away from the welding area during welding. This induced radiation includes shortwave radiation and can significantly impact the eyes and overall health; it's best to keep a safe distance from the welding point. When working at close range, take appropriate protective measures such as wearing respiratory protection, radiation protection clothing, and goggles.
